whmcsTools/servicecode.php

<?php

// this hook returns $addon->subscriptionid as $addon.code in smarty

if (!defined("WHMCS"))
    die("This file cannot be accessed directly");

add_hook('ClientAreaProductDetailsPreModuleTemplate', 1, function($vars) {

    logModuleCall(
        'ClientAreaProductDetailsPreModuleTemplate',
        __FUNCTION__,
        $vars,
        'debug',
        ''
    );

});